The present invention relates to a replacement endless track for a heavy duty tracked vehicle. Endless tracks are used on heavy duty vehicles such as tractors, bulldozers, and tanks. As shown in FIG. 1, such a vehicle includes an endless track drive system 2 made up of a closed loop endless track 3 in conjunction with the necessary sprocketed drive wheel 4 and any necessary supporting wheels, such as opposite end wheel 5 and idler wheels or rollers 6. The endless track is installed so as to pass around the wheels 4, 5 and 6. Of course, the tracked vehicle is further equipped with the necessary power source and controls to power the endless track drive system and thereby propel the vehicle over varying terrain as desired.
As seen in FIG. 2, one conventional endless track 3 consists of two parallel rails 7 each comprised of a plurality of rail blocks 7' linked together and supporting a plurality of metal grousers 8. Metal drive pins 9 between opposing rail blocks are engaged by the drive wheel sprocket to propel the vehicle. Drive pins 9 are typically driven into and retained by press fittings 10 in the rail blocks. Replaceable protective metal bushings 9' may be provided around drive pins 9 to protect the drive pins from wear, and a lubricant may be injected between drive pins 9 and bushings 9' from reservoirs in drive pins 9 to reduce friction. Examples of this type of track are disclosed, for example, in U.S. Pat. Nos. 2,823,082; 3,734,577; 3,955,855; 4,359,248; and 4,530,546. See also Caterpillar's Sealed and Lubricated Track brochure and U.S. Pat. No. 5,183,318.
As seen in FIG. 2A, another conventional track 3A consists of a plurality of central guide members 7A and a plurality of metal grousers 8A. The grousers 8A are held together by a plurality of drive units 9A disposed on the peripheral edges of the track 3A. The drive units 9A are engaged by drive wheel sprockets to propel the vehicle. Each drive unit 9A includes a pair of laterally extending pins 10A and a connecting member 12A. Laterally extending pins 10A of adjacent grousers are fitted into one of connecting members 12A.
The above-referenced conventional tracks have the disadvantages of being noisy and vibration prone, not sufficiently durable and/or not usable on road surfaces. This is because of the conventional configurations and use of metal parts. Accordingly, substantial efforts have been made to construct quieter, smoother operating and more durable tracks for tracked vehicles of rubber, polyurethane or other polymeric materials. See, e.g., Applicants'own U.S. Pat. Nos. 4,093,318; 4,569,561; 4,616,883; Re. 33,324; 4,844,560; 4,861,120; 4,884,852; 4,906,054; 5,005,921; 5,005,922; 5,020,865; and 5,040,282 (fully incorporated herein by reference). See also, e.g., U.S. Pat. No. 4,904,030 and PCT Publication No. WO 85/2824. However, these tracks and tracks like them suffer from the disadvantage that direct replacement of the above-described conventional metal tracks is not possible. In other words, some modification of the conventional tracked vehicle is necessary in order to accommodate these polymeric tracks. Moreover, further improvements in durability are still needed.
Thus, there remains a need for replacement endless vehicle tracks which overcome the foregoing problems.